Two of Endeavour's astronauts will return to their jobs as orbiting construction workers today, installing probes that will measure electrical potential surrounding the station and performing some added "warranty work" on solar array blankets that didn't stretch out completely on Sunday.

After carefully going through the plan with Mission Control on Wednesday and receiving descriptions and videotapes of fellow Astronaut David Wolf performing the additional task on the ground, Commander Brent Jett and his crew voiced optimism they could accomplish the new task.

Mission Specialists Joe Tanner and Carlos Noriega will float out the shuttle's hatch at 10:51 a.m. CST and move up to the top of the new solar array truss structure. Jett, Pilot Mike Bloomfield and Mission Specialist Marc Garneau will retract the mast extending the two blankets of the starboard solar array wing approximately two or three feet. Once the mast is shortened, Noriega will pull the slack in the tensioning cables through each take-up reel. Tanner will manually turn the spring-loaded tension reel until it reaches its limit and then will let the reel unwind by spring force while Noriega guides the cable onto the reel grooves. The outboard reel will be done first, followed by the inboard reel.

The 240-foot-long, 38-foot-wide solar array continues to function well, sending power to the International Space Station. The starboard array's cables apparently came out of the reel grooves when the wing was extended on Sunday. The port solar array wings were deployed to their full tension Monday using a modified deployment technique.

After the solar wing repair, Tanner and Noriega will install the Floating Potential Probe atop the P6 structure. The probe will measure the electrical potential of plasma around the station. Plasma Contactor Units already are at work on the solar array truss, emitting electrons that complete an electrical circuit and avoid the potential for arcing.

Expedition One Commander Bill Shepherd and cosmonauts Sergei Krikalev and Yuri Gidzenko awoke just after midnight CST and continued packing up items that will be returned to Earth aboard Endeavour. They also set up, but did not activate, a wireless instrumentation system that will attempt to measure and further model the structural integrity of the station as shuttle steering jets fire.

Humidity levels are coming down in the station after Wednesday's successful installation by the crew of a new air conditioning unit. The crew also replaced a malfunctioning fan in the Vozdukh carbon dioxide removal unit, bringing that life-support unit back on line. The hatch between the Zarya and Unity modules remains open indefinitely. The two crews are scheduled to meet inside Unity about 8:30 a.m. Friday.

Endeavour's crew was awakened at 6:06 a.m. CST to the sounds of the Beatles' "Here Comes the Sun," sent up for Joe Tanner. The station crew is scheduled to go to bed at 3:36 p.m. CST, and the shuttle crew will begin its sleep shift at 10:06 p.m.